In the process of learning a language, students naturallymake errors. The purpose of the present study is to examine the mechanism by which Japanese learners of English make errors, and how teachers of English should deal with the errors our students make in the classroom. First, we will look briefly at the language development of both young native speakers of English and classroom learners of English as a foreign language, with a special reference to errors they make in the process of learning. In the case of the latter, it should be noted that their errors mainly come from overgeneralization and negative transfer from their native language. We will then consider two approaches to the handling of learners'errors. In the Audio-lingual approach,errors are bad habits that should be corrected as soon as possible. The communicative approach, on the other hand, urges teachers totake a flexible attitude toward grammatical errors, especially local ones. Finally, we will examine Hendrickson's (1978) five crucial questions aboutcorrective feedback: (1) Should learners' errors be corrected ? (2) When should learners' errors be corrected ? (3) Which errors should be corrected ? (4) How should errors be corrected ?(5) Who should do the correcting ? Special attention will also be paid to implicit vs. explicit and input-providing vs. output-prompting ways of giving corrective feedback.